Conjunctivitis, allergic

There are three types of conjunctivitis: irritant, infective and allergic. Each type of conjunctivitis is caused by different factors.

Irritant conjunctivitis

Irritant conjunctivitis occurs when an irritant such as chlorine or an eyelash gets into your eyes. This can make your eyes sore, and if you rub them it can make the soreness even worse. Avoiding the irritant and not rubbing your eyes will help. However, if your eyes are very red and painful, you should seek medical help immediately.

Infective conjunctivitis

Infective conjunctivitis is caused by a virus or bacteria.

Allergic conjunctivitis

Allergic conjunctivitis is a common condition and is responsible for 15% of all eye-related problems recorded in GP surgeries. It occurs when your eye comes into contact with an 'allergen'. An allergen is a particular substance that makes your body's immune system react abnormally, causing irritation and inflammation in the affected body part. This is known as an allergic reaction. Common examples of allergens include pollen, dust mites and animal fur.

There are four main types of allergic conjunctivitis. The two most common types are outlined below.

  • Seasonal allergic conjunctivitis is the most common type of conjunctivitis, accounting for half of all allergic conjunctivitis cases. Symptoms recur at the same time each year and are most commonly triggered by pollen.
  • Perennial allergic conjunctivitis symptoms occur all year round and are usually present when you wake in the morning. The symptoms can be caused by a variety of allergens, such dust mites or animal fur.

The other two types of allergic conjunctivitis are less common. They are outlined below.

  • Contact dermatoconjunctivitis. Conjunctivitis with allergic dermatitis of the eyelids. Together with the usual symptoms of conjunctivitis, this condition causes the skin on your eyelids to become red, cracked, sore and inflamed (dermatitis). Eye drops are the most common cause of contact dermatoconjunctivitis.
  • Giant papillary conjunctivitis most commonly occurs in people using soft contact lenses. It may also develop following eye surgery. Your symptoms tend to progress slowly.

Allergic conjunctivitis is most commonly caused when your eyes come into contact with an allergen. An allergen is a particular substance that causes your body's immune system to react abnormally, causing pain, soreness and inflammation in the conjunctiva. This is known as an allergic reaction.

There are a variety of allergens that can cause allergic conjunctivitis which include:

  • pollen (hayfever),
  • dust mites,
  • make up,
  • animal fur, and
  • eye drops.

The most common allergen to cause allergic conjunctivitis is pollen, which is often accompanied by sneezing, and a blocked, or runny, nose. This is called seasonal allergic conjunctivitis. When it occurs with allergic rhinitis, it is commonly known as hayfever. Seasonal allergic conjunctivitis is more common in the spring and summer months when grass, trees and flowers are in pollen.

Contact lenses and eye drops

Contact dermatoconjunctivtis and giant papillary conjunctivitis are rare conditions that are often associated with the use of contact lenses and eye drops.

  • Contact dermatoconjunctivtis – is always associated with inflammation of the skin around the eye, and usually occurs in those using eye drops.
  • Giant papillary conjunctivitis – usually causes discomfort of your eyes when you put your contact lenses in and, as the condition develops, your lenses will feel more and more uncomfortable, and your eyes may become redder. It can also occasionally occur if you use hard contact lenses and following eye surgery.

There is no procedure or test to confirm allergic conjunctivitis. Your GP will usually be able to make a diagnosis by assessing your symptoms. Itching eyes is the most common symptom. Your GP will also ask about any other symptoms you may be experiencing. For example, if your allergic conjunctivitis is caused by pollen, you may also be experiencing sneezing and congestion.

Other conditions

Allergic conjunctivitis is one of several conditions which can cause your eyes to appear reddened. It is very important that your GP rules out any other conditions which may be causing your eyes to appear inflamed.

If you experience any of the following symptoms, you should see your GP immediately:

  • moderate to severe pain in your eyes,
  • photophobia (sensitivity to light)
  • disturbed vision, or
  • intense redness in your eyes.

It is very important for you to seek medical assistance if you experience these symptoms because it may be an indication that there is a more serious condition that is causing them. This is why it is important for your GP to rule out any other conditions which, if undiagnosed, may possibly cause serious complications.

Some conditions which may cause reddened eyes are outlined below.

  • Acute glaucoma – this is a rare form of glaucoma which causes a build-up of pressure in the eye. Symptoms of pain and loss of vision can develop very rapidly. If acute glaucoma is not treated, it can result in a permanent loss of vision.
  • Keratitis – this is when your cornea (the clear layer at the front of your eye that allows light to travel through your eye) becomes inflamed, and sometimes ulcerated. In severe cases, this can cause scarring of the cornea, which can lead to a permanent loss of vision.
  • Iritis – this condition causes your iris (the coloured part of your eye behind the cornea) to become inflamed. If iritis is not treated, it can cause the iris to start sticking to the front surface of the lens, which prevents fluid draining from the pupil. This can cause permanent damage to the eye.

Your GP will check to see that your symptoms are not being caused by a substance, or object, that it is irritating your eye. For example, your eyelashes may be rubbing against the surface of your eye, or you may have a small foreign body lodged beneath your eyelid.

Getting chlorine or shampoo in your eyes can also cause similar symptoms to allergic conjunctivitis. Your GP will also check that your condition is not being caused by an infection in the conjunctiva (infective conjunctivitis).


If you have severe symptoms of conjunctivitis, or your symptoms are getting worse, your GP may refer you to an eye specialist called an ophthalmologist.

If you develop giant papillary conjunctivitis as a result of recent eye surgery, you will be immediately referred to an ophthalmologist. This is to ensure that your eyes can be carefully monitored, and the best, most effective treatment given. If your GP suspects you have dermatoconjunctivitis, you may also be referred to an ophthalmologist so that the diagnosis can be confirmed.

The symptoms of allergic conjunctivitis usually affect both eyes. Your symptoms may appear very suddenly, often immediately after coming into contact with an allergen. In other cases, your symptoms will develop 24-48 hours after you have come into contact with the allergen.

The symptoms of allergic conjunctivitis may include:

  • Reddening of the eyes – is the most common symptom of allergic conjunctivitis. It occurs as a result of the irritation and widening of the tiny blood vessels in your conjunctiva (thin layer of skin inside your eyelids). If your eyes are very red and they are very painful, or if your vision is affected, or your eyes are extremely sensitive to light (photophobia), you should seek immediate medical assistance.
  • Itchy eyes.
  • Watering eyes – the conjunctiva contain thousands of cells that produce mucus, and tiny glands that produce tears. Irritation causes the glands to become overactive, so that they water more than usual.
  • Swollen eyelids.
  • Soreness and a slight burning sensation – your whole eye area may feel sore and tender from the inflammation, and you may feel a slight burning sensation in your eyes in general.

If you have seasonal allergic conjunctivitis, your symptoms may appear at certain times of the year – for example, in the spring or summer. The symptoms of perennial allergic conjunctivitis can occur all year round, and may be worse at certain times of the day, such as first thing in the morning.

Dry, red, and cracked skin on your eyelids that is sore and painful, may indicate that you have contact dermatoconjunctivitis. The symptoms of both contact dermatoconjunctivitis, and giant papillary conjunctivitis, may appear at any time.


If your allergic conjunctivitis requires rapid relief, your GP is most likely to prescribe a medicine known as an antihistamine. This medicine may have to be taken orally, or you may have to apply it directly to the eye in the form of eye drops.

Oral antihistamines that are commonly prescribed include cetirizine, fexofenadine and loratadine. You will usually only have to take an oral antihistamine once a day. Commonly prescribed eye drops include azelastine, emedastine and ketoifen. These eye drops normally have to be used two to three times a day.

Antihistamines should help to reduce the inflammation in your eyes. They should also be able to ease related symptoms, such as sneezing and rashes. Antihistamines rarely cause side effects. However, in some cases, oral antihistamines can cause drowsiness, although this tends to occur less commonly with newer types of antihistamines than with older types.

If you are taking antihistamines for the first time, it may be advisable to avoid activities such as driving, or operating machinery, until you know how the medicine affects you.

Mast cell stabilizers

Mast cell stabilizers may also be prescribed to treat allergic conjunctivitis. Unlike antihistamines, they are more effective at controlling your symptoms over a longer period of time, rather that providing rapid relief and it may take several weeks before you feel the effects of this type of medicine. You may be prescribed an antihistamine to take at the same time as a mast cell stabilizer, so that your symptoms can be controlled while you are waiting for the mast cell stabilizer to take effect. Mast cell stabilizers that are commonly prescribed, include lodoxamide and nedocromil. These medications are in the form of eye drops.


If your symptoms of allergic conjunctivitis are particularly severe, and the diagnosis has been confirmed, you may be prescribed a short course of an oral (by mouth) corticosteroid. However, an oral corticosteroid is very rarely needed and is not normally prescribed unless absolutely necessary.